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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-911CD800-2D1B-5D7B-A67C-66E01F91062C" xml:lang="en"><title>Heaps</title><shortdesc>The main thread of a process has a memory chunk that contains the

    13 thread's heap. A program's request for memory is allocated from this heap.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>Each thread has a chunk which contains that thread's program stack. For

    15 the main thread of a process, this chunk also contains the thread's heap.

    16 A program's request for memory is allocated from this heap. For example, a

    17 code fragment such as: </p>

    18 <codeblock id="GUID-ED3A8BC9-7601-5035-B422-ED80E5504867" xml:space="preserve">CArrayFixFlat&lt;...&gt;* fixflat;

    19 ...

    20 fixflat = new (ELeave) CArrayFixFlat&lt;...&gt;(3);</codeblock>

    21 <p>causes a portion of memory to be allocated from the heap and its address

    22 returned to the caller. Memory from the heap must be explicitly requested

    23 and, importantly, explicitly freed by the program. </p>

    24 <p>If a process creates additional threads, then a new chunk is created for

    25 each new thread. Each chunk contains the thread's stack; if a new thread is

    26 not sharing an existing heap, then the chunk also contains a new heap. </p>

    27 <p>When a new thread is created, either: </p>

    28 <ul>

    29 <li id="GUID-C915A4D8-70D9-55B4-A16F-9729B1F8D94B"><p>a new heap is created

    30 for it </p> </li>

    31 <li id="GUID-E72B8DF5-CB52-5333-9D3E-EFDBAFE6CB59"><p>it uses the creating

    32 thread's heap </p> </li>

    33 <li id="GUID-20C6F186-6EF6-511E-9291-3273CA930B5D"><p>it uses an explicitly

    34 referenced heap. </p> </li>

    35 </ul>

    36 <p>A thread gets the handle to its heap by calling <xref href="GUID-C197C9A7-EA05-3F24-9854-542E984C612D.dita#GUID-C197C9A7-EA05-3F24-9854-542E984C612D/GUID-42AC433D-1C9C-3AC6-8640-EB1A7BA876B5"><apiname>User::Heap()</apiname></xref>. </p>

    37 <p>See <xref href="GUID-D557CC2C-C045-5818-B2F7-9BD8BC39257D.dita">Address Space

    38 and Process</xref> for more background on chunks and heaps.</p>

    39 </conbody></concept>